Extinct radionuclide
Encyclopedia
An extinct radionuclide
is one that scientists believe was formed by primordial processes, such as stellar nucleogenesis in the supernova
(s) that contributed radioisotopes to the early solar system, about 4.6 billion years ago. Generally, radioisotopes with a decay half-life
shorter than about 100 million years are not found in nature, except for those generated continuously by a natural process, such as cosmic rays, or a decay chain
of much longer lived isotopes, such as uranium
or thorium
. Other short-lived isotopes are thus seen only as extinct radionuclides, whose former existence is inferred now from a superabundance of their stable decay products.
Examples of extinct radionuclides include iodine-129
(the first to be noted in 1960, and inferred from excess xenon-129
concentrations in meteorites, in the xenon-iodine dating system), aluminium-26
(also inferred from extra magnesium-26 found in meteorites), and iron-60.
Some notable isotopes with shorter lives still being produced on Earth include:
Radioactives with half-lives shorter than one million years are also produced: for example, carbon-14
by cosmic ray production in the atmosphere (half-life 5730 years).
Radionuclide
A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...
is one that scientists believe was formed by primordial processes, such as stellar nucleogenesis in the supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
(s) that contributed radioisotopes to the early solar system, about 4.6 billion years ago. Generally, radioisotopes with a decay half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
shorter than about 100 million years are not found in nature, except for those generated continuously by a natural process, such as cosmic rays, or a decay chain
Decay chain
In nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive decay products as a chained series of transformations...
of much longer lived isotopes, such as uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
or thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
. Other short-lived isotopes are thus seen only as extinct radionuclides, whose former existence is inferred now from a superabundance of their stable decay products.
Examples of extinct radionuclides include iodine-129
Iodine-129
Iodine-129 is long-lived radioisotope of iodine which occurs naturally, but also is of special interest in the monitoring and effects of man-made nuclear fission decay products, where it serves as both tracer and potential radiological contaminant....
(the first to be noted in 1960, and inferred from excess xenon-129
Isotopes of xenon
Naturally occurring xenon is made of nine stable isotopes. Xenon has the second highest number of stable isotopes. Only tin, with 10 stable isotopes, has more...
concentrations in meteorites, in the xenon-iodine dating system), aluminium-26
Isotopes of aluminium
Aluminium has 22 known isotopes from 21Al to 42Al and 4 known isomers. Only 27Al and 26Al occur naturally, however 27Al has a natural abundance of 99.9+ %. Other than 26Al, all radioisotopes have half-lives under 7 minutes, most under a second. Standard atomic mass is 26.9815386 u...
(also inferred from extra magnesium-26 found in meteorites), and iron-60.
List of extinct radionuclides
A partial list of radionuclides not found in nature, but for which decay products exist:| Isotope | Halflife (Myr Myr The symbol myr was formerly used in English-language geology, and remains as the standard usage in astronomy, as a unit of one million years.It is an abbreviation for 'million years' and lower case is used in geology, while upper case is used in astronomy.... ) |
|---|---|
| Samarium-146 Isotopes of samarium Naturally occurring samarium is composed of five stable isotopes, 144Sm, 149Sm, 150Sm, 152Sm and 154Sm, and two extremely long-lived radioisotopes, 147Sm and 148Sm , with 152Sm being the most abundant... |
103 |
| Niobium-92 Isotopes of niobium Naturally occurring niobium , element 41, is composed of one stable isotope . 93Nb is the lightest nuclide theoretically susceptible to spontaneous fission, and although this has never been observed, it makes niobium theoretically the lightest element with no stable isotope... |
34.7 |
| Curium-247 Isotopes of curium Curium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope synthesized was 242Cm in 1944.... |
16 |
| Lead-205 Isotopes of lead Lead has four stable isotopes: 204Pb, 206Pb, 207Pb, 208Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide. The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains called the uranium series , the actinium series, and the thorium... |
15 |
| Hafnium-182 Isotopes of hafnium Natural hafnium consists of five stable isotopes and one very long-lived radioisotope, 174Hf, with a half-life of 2×1015 years. In addition, there are 30 other known radionuclides, the most stable of which is 182Hf with a half-life of 8.9×106 years. No other radioisotope has a... |
9 |
| Palladium-107 | 7 |
| Caesium-135 | 3 |
| Technetium-97 Isotopes of technetium Technetium is the first of the two elements in the first 82 that have no stable isotopes ; the other such element is promethium. It is primarily artificial, only trace quantities existing in nature produced by spontaneous fission or neutron capture by molybdenum... |
3 |
| Gadolinium-150 Isotopes of gadolinium Naturally occurring gadolinium is composed of 6 stable isotopes, 154Gd, 155Gd, 156Gd, 157Gd, 158Gd and 160Gd, and 1 radioisotope, 152Gd, with 158Gd being the most abundant... |
2 |
| Zirconium-93 | 2 |
| Technetium-98 Isotopes of technetium Technetium is the first of the two elements in the first 82 that have no stable isotopes ; the other such element is promethium. It is primarily artificial, only trace quantities existing in nature produced by spontaneous fission or neutron capture by molybdenum... |
2 |
| Dysprosium-154 Isotopes of dysprosium Naturally occurring dysprosium is composed of 7 stable isotopes, 156Dy, 158Dy, 160Dy, 161Dy, 162Dy, 163Dy and 164Dy, with 164Dy being the most abundant . 29 radioisotopes have been characterized, with the most stable being 154Dy with a half-life of 3.0 million years, 159Dy with a half-life of... |
1 |
Some notable isotopes with shorter lives still being produced on Earth include:
- Manganese-53Isotopes of manganeseNaturally occurring manganese is composed of 1 stable isotope; 55Mn. 25 radioisotopes have been characterized with the most stable being 53Mn with a half-life of 3.7 million years, 54Mn with a half-life of 312.3 days, and 52Mn with a half-life of 5.591 days...
and beryllium-10Beryllium-10Beryllium-10 is a radioactive isotope of beryllium. It is formed mainly by cosmic ray spallation. Be-10 has a half-life of 1.36 × 106 years, and decays by beta decay to stable Boron-10 with a maximum energy of 556.2 keV....
are produced by cosmic ray spallationCosmic ray spallationCosmic ray spallation is a form of naturally occurring nuclear fission and nucleosynthesis. It refers to the formation of elements from the impact of cosmic rays on an object. Cosmic rays are highly energetic charged particles from outside of Earth ranging from protons, alpha particles, and nuclei...
on dust in the upper atmosphere. - Uranium-236Uranium-236- See also :* Depleted uranium* Uranium market* Nuclear reprocessing* United States Enrichment Corporation* Nuclear fuel cycle* Nuclear power-External links:* *...
is produced in uranium ores by neutrons from other radioactives. - Iodine-129Iodine-129Iodine-129 is long-lived radioisotope of iodine which occurs naturally, but also is of special interest in the monitoring and effects of man-made nuclear fission decay products, where it serves as both tracer and potential radiological contaminant....
is produced from tellurium-130 by cosmic-ray muons and from cosmic ray spallation of stable xenon isotopes in the atmosphere.
Radioactives with half-lives shorter than one million years are also produced: for example, carbon-14
Carbon-14
Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological...
by cosmic ray production in the atmosphere (half-life 5730 years).
See also
- Isotopes
- Iodine-129Iodine-129Iodine-129 is long-lived radioisotope of iodine which occurs naturally, but also is of special interest in the monitoring and effects of man-made nuclear fission decay products, where it serves as both tracer and potential radiological contaminant....
- Radiometric datingRadiometric datingRadiometric dating is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates...
- List of nuclides which includes a listing for radionuclides in order of half life